Field of the Invention
The present invention relates to a direct injection internal combustion engine having an injector for directly injecting fuel into a combustion chamber thereof, and particularly to the direct injection internal combustion engine in which the fuel injection by the injector is performed three times in one combustion cycle.
Description of the Related Art
Japanese Patent Laid-open Publication No. 2007-177731 (JP'731) discloses a direct injection internal combustion engine in which the fuel injection by the injector is performed three times in one combustion cycle. Specifically, all of three injections are performed in the intake stroke of the object cylinder wherein the first injection is performed in the range from 0 deg. to 60 deg. after the top dead center at which the intake stroke starts (hereinafter referred to simply as “top dead center”), the second injection is performed in the range from 60 deg. to 140 deg. after the top dead center, and the third injection is performed from 140 deg. to 180 deg. after the top dead center.
In the case where the required fuel amount is supplied with only one fuel injection in the intake stroke, there exists a problem that an increasing amount of smoke and/or unburned gases becomes large. Accordingly, in the direct injection internal combustion engine shown in JP'731, the fuel injection is performed with three-divided injections. However, since the first injection is performed during the first half of the intake stroke, a generation amount of soot (smoke) is comparatively large when the temperature of the engine is low (before completion of the warming up of the engine). It is therefore desired to reduce the generation amount of soot.